BALCH: LIST OF MARINE MOLLUSCA. 
155 
Akcidae. 
Area transversa Say. Smith and Prime (’TO), p. 384. Sca- 
pharca t. Verrill (’73), p. 691. S. 
Common on shelly bottom, 2 fatli. and below. 
Area pexata Say. Smith and Prime (’TO), p. 385. Argina p. 
Verrill (’73), p. 692. S. 
Occurs with the last species but not one fifth as common. Per¬ 
kins (’69) notes the opposite condition at New Haven. Neither of 
these “ bloody-clams ” appears to have the deep-burrowing habit 
which Lankester’s explanation (’73) of the presence of haemoglobin 
in the blood calls for. 
Mytilidae. 
Mytilus eclulis LinnA Smith and Prime (’70), p. 386. Verrill 
(’73), p. 692. N. 
Abundant everywhere, but the great “mussel-ridges ” so charac¬ 
teristic of some waters do not occur; Gould’s var . pellucidus is not 
uncommon. 
Modiola modiolus (Linne). Verrill (73), p. 693. Mytilus m. 
Smith and Prime (’70), p. 386. N. 
No live specimens were taken, but doubtless the species occurs 
in the harbor as very fresh valves were tolerably common in the 
dredge at certain spots. 
Modiola plieatula Lam. Verrill (’73), p. 693. Mytilus p. 
Smith and Prime (’70), p. 386. S. 
Abundant everywhere, especially about salt marshes. 
Specimens from a certain marsh near Lloyd’s Harbor show curi¬ 
ous distortion and erosion effects so constant as to resemble a real 
variety; but doubtless the erosion, which is sharply confined to the 
beaks which are buried in the soil, is due to the presence of humous 
or other acids and probably the distortion is due to the same cause. 
In the same marsh the clam shells were very curiously distorted; cf. 
infra. 
